Protecting ferrous metals from corrosion



such as mixtures of crude oil and brine.

United States Patent PROTECTING FERROUS METALS FROM CORROSION William F. Oxford, In, Beaumont, Tex., assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New ersey No Drawing. Application May 10, 1956 Serial No. 583,901

10 Claims. (Cl. 252-855) This invention relates to inhibiting corrosion of ferrous metal surfaces.

Protection of metal surfaces from corrosion is an important factor in many fields of technology. One manner of providing such protection is by use of a corrosion inhibitor which forms an adsorbed protective film on a metal surface, which film resists attack of the surface by corrosive agents in fluids with which the surface would otherwise come in direct contact. The present invention provides corrosion inhibition, by means of adsorbed protective films of certain amine salts, which is remarkably effective even when the amine salts are used in quite small amounts.

One application of corrosion inhibition which is of great importance in petroleum production is the inhibition of corrosion normally caused by corrosive oil well fluids Corrosion of metal tubing, casing, pumps, and other equipment used in producing oil from wells is a particularly difiicult problem in petroleum production. The mixtures of crude oil and brine which are produced in most wells are highly corrosive to the metals of which such equipment is commonly constructed, particularly when the brine contains hydrogen sulfide, carbon dioxide, or other acidic materials.

According to the present invention, corrosion of ferrous metal surfaces is inhibited by forming an adsorbed protective film on the metal surface of a petroleum naphthenic acid salt of (l) a compound having the formula RNH[(CH ),,,NH],,H where R is hydrogen or the hydrocarbon radical of a naturally occurring fatty acid RCOOH, where m is an integer from 2 to and preferably 2 or 3, and where n is an integer from 1 to 10, (2) an N-hydroxyalkyl derivative of a compound having that formula, or (3) and N-hydroxyalkyl derivative of ammonia or an alkyl monoamine having 1 to 5 carbon atoms, the latter derivative having a nitrogen atom to which less than two hydrogen atoms are directly attached, and preferably having molecular weight greater than about 125. The hydroxyalkyl derivatives can be prepared in known manner by reaction of an alkylene oxide, e.g. ethylene oxide, propylene oxide, 1,2-epoxybutane, 1-methyl-2,3-epoxybutane, etc. with the nitrogen compound in question. The hydroxyalkyl groups in the derivative contain a total of 2 to carbon atoms inclusive, which may be contained in one or more hydroxyalkyl groups. A hydroxyalkyl group, for the purpose of the present invention, is to be considered as including groups containing ether linkages, e.g. -CH CH OCH CH OH, etc.

When n in the above formula is greater than 5, R is preferably hydrogen or an alkyl group having less than 5 carbon atoms. When n is 5 or less, R may in some instances be an alkyl group having a greater number of carbon atoms. When n is 1, R preferably has 12 to 20 carbon atoms. In the latter case, R can advantageously be the hydrocarbon radical of a natural fatty acid mixture RCOOH, e.g. tallow acids, soya acids, cocoa acids, etc., a mixture of amines therefore being employed.

In one embodiment, the invention involves the use, to

inhibit corrosion, of a petroleum naphthenic acid salt of a polyamine residue obtained in the reaction of an alkylene dihalide, e.g. ethylene dichloride, with a nitrogen base, e.g. ammonia, to produce alkylene amines, after distillation of lower boiling alkylene amines, for example those having the formula NH (CH CH NH),,H where n is 1, 1 to 2, 1 to 3, 1 to 4, etc. Such residue may be blended back, if desired, with a distillate alkylene amine.

In a further embodiment, a petroleum naphthenic acid salt of an alkanolamine residue obtained in the reaction of an alkylene oxide, e.g. ethylene oxide, with a nitrogen base, e.g. ammonia, to produce alkanolamines is used. The residue may be one obtained for example after distillation of lower boiling ethanolamines such as ethanolamine, or ethanolamine and diethanolamine, etc. The residue contains, in one embodiment, polymers such as dimers and trimers of triethanolamine. Such polymers are to be regarded as N-hydroxyalkyl derivatives of ammonia, for the purposes of the present invention.

Suitable amines for use according to the invention include the following: ethylene diamine, N-butyl ethylene diamine, N-hexadecyl trimethylene, diamine, N-octadecyl tetrarnethylene diamine, diethylene triamine, N-methyl triethylene tetramine, N-hexyl tetraethylene pentamine, N- octadecyl tetraethylene pentamine, diethanolamine, triethanolamine, l-hydroxyethylamino butane, diethyl ethanolamine, N-hydroxyethyl ethylene diamine, N,N'-di(hydroxyethyl) ethylene diamine, N,N'-di(hydroxyethyl)-N- octadecyl ethylene diamine, N-ethoxyethanol-N'-octadecyl ethylene diamine, etc. Mixtures of amines can also be employed.

Petroleum naphthenic acids in general can be used to prepare compounds for use according to the invention. Such acids preferably are mixtures boiling through a range of at least 75 Fahrenheit degrees, and frequently the mixtures boil through a range of at least 150 Fahrenheit degrees. Relatively high molecular weight naphthenic acids, having saponification number for example within the range from 120 to 200 mg. of KOH per gram, are used to advantage, but lower molecular weight acids, having saponification number for example within the range from 200 to 320, can also be used.

In one embodiment of the invention, a highly effective means is provided of combating corrosion by fluids produced in oil wells, including gas wells and gas condensate wells. This is accomplished for example, by introducing an inhibitor according to the invention into the normally corrosive well fluids. The inhibitor can be commingled with the well fluids in any suitable manner, e.g. by introducing it, either alone or dissolved in a suitable solvent such as an aromatic hydrocarbon solvent, into the well tubing or into the annulus between the tubing and casing. The inhibitor can alternatively be incorporated in a solid stick inhibitor containing microcrystalline wax or other suitable material. The injection practices which are known for use with other organic inhibitors are generally suitable for use with the present inhibitor. Preferably, the inhibitor is added to the corrosive well fluids in amounts of 25 to 1000 ppm. based on the well fluids, more preferably to 500-p.p.m. I

The corrosion inhibitors according to the invention are useful in inhibition generally of ferrous metal surfaces. Thus, for example, they are useful in'various petroleum refinery operations wherein corrosion normally occurs, often causing severe problems. By way of illustration, in gas plant operations, where a normally liquid hydrocarbon material such as kerosene is used as sponge oil to absorb hydrocarbon constituents from gas streams, the presence of corrosive agents such as hydrogen sulfide, elemental sulfur, inorganic sulfates and sulfides, etc. frequently causes, in the presence of water, severe corrosion problems in heat exchangers and other ferrous metal equipment with which the sponge oil comes in contact. In typical operation, for example, the sponge oil may be subjected to steam stripping to remove absorbed constituents and then, prior to reuse as absorbing agent, used as an indirect heating medium for sponge oil containing absorbed constituents prior to introduction of the latter into the stripper. Corrosion of heat exchanger surfaces by the lean sponge oil at a temperature of about 350 F. for example frequently occurs in such operation; formation of objectionable iron sulfate deposits is also a problem frequently associated with corrosion in such operation. According to one embodiment of the invention, a corrosion inhibitor as described herein is introduced into the circulating sponge oil, preferably into the lean oil while passing from the stripper to the heat exchanger in order to reduce corrosion and deposit formation to suitably low levels.

The corrosion inhibition method according to the in vention is also useful in other petroleum refinery operations and in operations in other industries where normally corrosive fluids are contacted with ferrous metal surfaces.

The following examples illustrate the invention:

Example I A mixture of salts produced by neutralizing petroleum naphthenic acids with a diamine material known by the trade mark Duomeen T was prepared and tested for its ability to inhibit corrosion by fluids similar to those produced in oil Wells.

Duomeen T comprises a mixture of diamines having the formula RNHCH CH CI-l NH where R is a hydrocarbon radical derived from tallow, the average molecular weight of the mixture of diamines being 320. Since the mixture of diamines is not pure, the combining weight of Duomeen T is about 400.

The naphthenic acids employed conformed in preparation and properties to those sold commercially under the trade mark Sunaptic Acids A. Typical properties for such acids are the following: acid number 178 mg. of KOH per gram, average molecular weight 297, average molecular formula C H O average type formula C H O and distillation range 315 to 485 F./2mm. Hg (-95% p The mixture of salts was produced by stirring together the naphthenic acids with the mixture of diamines, thereby to produce a mixture of diamine dinaphtbenates having average molecular weight of about 914. Slightly more than two moles of naphthenic acids per 400 parts by weight of Duomeen T were employed. The resulting mixture of salts varied from one salt to the next not only in the diamine residue but also in the acid residue since the naphthenic acids used were also a mixture of acids having varying molecular weight and chemical structure.

The mixture of salts was tested as an inhibitor of corrosion by corrosive materials similar to those in an oil well. Approximately equal volumes of a severely corrosive sour West Texas crude saturated with hydrogen sulfide, and of brine saturated with hydrogen sulfide and carbon dioxide were placed in a bottle, together with amounts of the salt mixture as indicated in the table below, expressed as parts per million based on the sum of the volumes of oil and brine. A cleaned and weighed A rod of mild steel was placed in the bottle, and the latter was sealed. The liquids nearly filled the bottle, the remaining fluid being largely air. The bottle was placed on the periphery of a drum which was rotated at a rate of about 100 revolutions per minute for a period of 24 hours. The test was carried out at room temperature. The steel rod was then removed, electrolytically cleaned, and weighed to determine the weight loss from corrosion by the oil and brine. This weight loss was compared with that obtained in a blank run with no inhibitor, and the percent reduction in weight loss by use of the in- 4 hibitor determined. The following table shows the percent reduction at various inhibitor concentrations.

This example shows that a large reduction in corrosion is produced by admixing with the corrosive liquids a mixture of salts of petroleum naphthenic acids with N-substituted propylene diamine, wherein the N-substituent is a hydrocarbon radical derived from tallow.

Example II Duomeen T dinaphthenates were compared with Duomeen T dioleate as corrosion inhibitors according to the test procedure described in Example I.

The naphthenic acids employed in the preparation of the Duomeen T dinaphtbenates conformed in preparation and properties to those sold commercially under the trademark Sunaptic Acids B. Typical properties for such acids are the following: acid number 159 mg. of KOH per gram, average molecular weight 330, average molecular formula C21H37O2, average type formula C I-I O and distillation range 287 to 530 F./2 mm. Hg (098%).

The Duomeen T dinaphtbenates were prepared by reacting 660 parts by weight of the naphthenic acids with slightly less than 400 parts by Weight of Duomeen T. The Duomeen T dioleate was presumably prepared by reacting 565 parts by weight of oleic acid with slightly less than 400 parts by weight of Duomeen T.

The following table shows the results obtained:

Percent Reduction in Weight Loss Concentration, p.p.m.

Duomeen Duomeen T Dinaph- T dioleate thenates This example indicates that dioleate salts. of the aliphatic diamines involved are ineffective to inhibit corrosion under the test conditions unless used in amounts greater than p.p.m., whereas the corresponding dinaphthenate salts give a large measure of protection against corrosion when used in 100 ppm. concentration, and give some protection even in amounts as small as 33 ppm.

Example 111 Duomeen T mononaphthenates were tested as corrosion inhibitors according to the test procedure described in Example I.

The naphthenic acids employed in the preparation of the Duomeen T mononaphthenates conformed in preparation and properties to those sold commercially as Sunaptic Acids C. Typical properties for such acids are the following: acid number 122 mg. of KOH per gram, average molecular weight 415, average molecular formula C H O average type formula C H O and distillation range 408 to 596 F./2 mm. Hg (095%).

The Duomeen T mononaphthenates were prepared by reacting 415 parts by weight of the naphthenic acids with slightly more than 400 parts by weight of Duomeen T...

- The following table shows the results obtained:

Percent reduction in weight loss 99.5

Concentration, p.p.m.

A mixture of salts producetd by neutralizing petroleum naphthenic acids with a commercial product known by the trademark Polyamine H Special was tested as a corrosion inhibitor according to the method of Example I.

Polyamine H Special is a mixture of 25 weight percent diethylene triamine and 75 weight percent of a residue obtained in the preparation of polyalkylene polyamines by the reaction of ethylene dichloride and ammonia; the mixture has an equivalent weight of 40. The residue contains those constituents of the reaction products which are higher boiling than tetraethylene pentamine. The residue probably comprises polyalkylene polyamines having the formula H N(CH Gl-I NH),,H wherein n is an integer greater than 4; it also comprises compounds having tertiary nitrogen atoms, as in the case where an aminoethyl group attaches to a secondary nitrogen atom of triethylene tetramine or a higher polyalkylene polyamine; the residue also comprises cyclic amines, derivatives of piperazine, formed by cyclization of compounds containing at least two nitrogen atoms and two ethylene groups.

The naphthenic acids used were generally similar to those described in Example I and had acid number of about 170 mg. of KOH per gram.

The mixture of salts was produced by stirring together 89 grams of the naphthenic acids with 11 grams of the polyamines, thereby to produce a mixture of polyamine naphthenates.

The mixture of salts was tested in 1000 p.p.m. concentration as a corrosion inhibitor according to the procedure described in Example I. The mixture was also tested in 500 and 200 p.p.m. concentration according to the NACE Static Test, a somewhat similar procedure though not involving agitation of the well fluids during the test. The following table shows the results obtained:

Percent reduction Concentration, p.p.m.: in weight loss Example V Ethoxylated Duomeen T dinaphthenates were tested as corrosion inhibitors according to the test procedure described in Example I. The naphthenic acids employed were similar to those described in Example II. The

ethoxylated Duomeen T dinaphthenates were preparedby reaction 660 parts by weight of the naphthenic acids with slightly less than 488 parts by weight of ethoxylated Duomeen T, the latter having been prepared by reacting two moles of ethylene oxide with one mole of Duomeen T.

The following table shows the results obtained:

Percent reduction Concentration, p.p.m.: in weight loss This example shows that the ethoxylated Duomeen T dinaphthenates have very good inhibiting properties, particularly when used in concentrations of 100 p.p.m. or greater. By comparison with the nonethoxylated Duo meen T'dinaphthenates of Example II, the ethoxylated dinaphthenates appeanto be somewhat superior .in some, relatively-high concentrations, but inferior at lower concentrations.

Example VI A mixture of salts produced by neutralizing petroleum naphthenic acids with a material known by "the'trademark Polyamine T was tested as a corrosion inhibitor according to the method of Example I. v

Polyamine T is a residue obtained in the preparation of ethanolamines by the reaction of ethylene oxide and ammonia. The residue typically has specific gravity at 20/20 F. of 1.12- to 1.16 and equivalent weight of to 165, and contains 20 to 30 percent triethanolamine. The other components are probably products of reaction of ethanolamines with ethylene oxide, or with each other in the presence of oxygen.

The naphthenic acids used were generally similar to those described in Example I and has acid number of about mg. of KOH per gram.

The mixture of salts was produced by stirring together 66 grams of the naphthenic acids with 34 grams of Polyamine T, thereby to produce a mixture of ethanolamine naphthenates.

The mixture of salts was tested as a corrosion inhibitor according to the procedures described in Example IV. The following results were obtained:

Percent reduction Concentration, p.p;m.: in weight loss Example VII Duomeen T mononaphthenates and dinaphthenates were prepared from each of the three naphthenic acid fractions described in Examples I, II and III, and the effectiveness of the six materials as inhibitors of corrosion normally caused by oil well fluids was compared with the effectiveness for such purpose of six materials obtained by preparing Duomeen T mononaphthenates and dinaphthenates of each of three naphthenic acid fractions, each fraction having an average of 15 or 16 carbon atoms per molecule, as compared with the 19 to 28 carbon atoms of the naphthenic acids used in Examples I, II and III. The following table shows a comparison of the average protection provided by the six higher 7 molecular weight salts and by the six lower molecular weight salts:

Percent Protection These results show that salts prepared from the higher molecular weight acids according to the invention show substantial superiority, as well corrosion inhibitors at 100 ppm, to salts prepared from lower molecular weight naphthenic acids, and great superiority to the latter salts as well corrosion inhibitors at 50 p.p.m.

Polyamine salts of naphthenic acids employed accord ing to the invention can be neutralized partially with naphthenic acids and partially with another acidic material, e.g. phosphoric acid, acetic acid, stearic acid, oleic acid, etc. Such partial naphthenate salts, e.g. Duomeen T. mononaphthenate monooleate, are superior to salts such as Duomeen T dioleate in a manner similar to that noted in Example II with regard to Duomeen T dinaphthenates.

In copending application Serial No. 514,371 filed June 9, 1955 by the present inventor, certain of the compounds the use of which as corrosion inhibitors for oil well fluids is disclosed and claimed herein, are claimed as new compositions of matter.

This application is a continuation-in-part of copending application Serial No. 486,277 filed February 4, 1955, now abandoned by the present inventor.

The invention claimed is:

1. Method for protecting ferrous metals from corrosion which comprises forming, in the presence of water and corrosive material selected from the group consisting of hydrogen sulfiide, carbon dioxide, sulfur, inorganic sulfates, and inorganic sulfides, a protective film on a ferrous metal surface of a petroleum naphthenic acid salt of a material selected from the group consisting of a compound having the formula RNH[(CH ),,,NH],,H where R is selected from the group consisting'of hydrogen and the hydrocarbon radical of a naturally occurring fatty acidRCOOH, where m is an integer from 2 to 5, and where n is an integer from 1 to 10, an N-hydroxyalkyl derivative of said compound wherein the hydroxyalkyl groups contain a total of 2 to carbon atoms, and an ethanolamine residue obtained in the reaction of ethylene oxide and ammonia to produce ethanolamines, after distillation of lower boiling ethanolamines from the reaction products, said residuehaving equivalent Weight within the approximate range from 145 to 165.

2. Method for inhibiting corrosion of ferrous metals by oil well fluids which comprises: introducing into normally corrosive oil well fluids, which come into contact with ferrous metals, a petroleum naphthenic acid salt of a material selected fromthe group consisting of a compound having the formula RNH[(CH ),,,NH],,H where R is selected from the group consisting of hydrogen and the hydrocarbon radical of a naturally occurring fatty acid RCOOH, where m is an integer from 2 to 5, and

where his an integer from 1 to 10, an N-hydroxyalkyl derivative of said compound wherein the hydroxyalkyl groups contain a total of 2 to 10 carbon atoms, and an ethanolamine residue obtained in the reaction of ethylene oxide and ammonia to produce ethanolamines, after distillation of lower boiling ethanolamines from the reaction products, said r'esidu'e having equivalent weight within the approximate range from 145 to 165.

3; Method according to claim 2 wherein said compound has the formula RNH(CH ),,,NH where R is the hydrocarbon radical of a naturally occurring fatty acid R'COOH'having 12' to 20 carbon atoms, and m is an integer from 2 to 5.

4. Method according to claim 2 wherein said compound has the formula NH (CH CH NH),,H, where n is an integer from 1 to 10.

5. Method according to claim 2 wherein said naphthenic acids have acid number within the range from to 320 mg. of KOH per gram.

6. Method according to claim 3 wherein m is 3 and RCOOH is a mixture of fatty acids derived from tallow.

7. Method according to claim 5 wherein the acid number is less than 200 mg. of KOH per gram.

8. Method for inhibiting corrosion of ferrous metals by oil well fluids which comprises: introducing into normally corrosive oil well fluids, which come into contact with ferrous metals, a petroleum naphthenic acid salt of a polyamine residue obtained in the reaction of ethylene dichloride and ammonia to produce ethylene amines, after distillation of lower boiling ethylene amines from the reaction products.

9. Method for inhibiting corrosion of ferrous metals by oil well fluids which comprises: introducing into normally corrosive oil well fluids, which come into contact with ferrous metals, a petroleum naphthenic acid salt of an ethanolamine residue obtained in the reaction of ethylene oxide and ammonia to produce ethanolamines, after distillation of lower boiling ethanolamines from the reaction products, said residue having equivalent weight within the approximate range from to 165.

10. Method for inhibiting corrosion of ferrous metals by oil well fluids which comprises: introducing into normally corrosive oil well fluids, which come into contact with ferrous metals, petroleum naphthenic acid salts of compounds having the formula RNHCH CH CH NH where R is the hydrocarbon radical of a naturally occurring fatty acid RCOOH' having 12 to 20 carbon atoms, the average number of carbon atoms in the naphthenic acids being within the range from 19 to 28.

References Cited in the file of this patent UNITED STATES PATENTS 2,430,951 Roualt Nov. 18, 1947 2,587,546 Matuszak Feb. 26, 1952 2,640,029 Blair et al. May 26, 1953 2,599,385 Gross et a1. June 3, 1952 2,640,029 Blair et al. May 26, 1953 2,643,227 Hughes et al June 23, 1953 2,736,658 Pfohl et al. Feb. 28, 1956 2,758,086 Stuart et al. a Aug. 7, 1956 2,798,045 Buck et al. July 2, 1957 2,818,383 Jolly Dec. 31, 1957 

1. METHOD FOR PROTECTING FERROUS METALS FROM CORROSION WHICH COMPRISES FORMING, IN THE PRESENCE OF WATER AND CORROSIVE MATERIAL SELECTED FROM THE GROUP CONSISTING OF HYDROGEN SULFIDE, CARBON DIOXIDE, SULFUR, INORGANIC SULFATES, AND INORGANIC SULFIDES, A PROTECTIVE FILM ON A FERROUS METAL SURFACE OF A PETROLUEM NAPHTHENIC ACID SALT OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF A COMPOUND HAVING THE FORMULA RNH( (CH2)MNH)NH WHERE R IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND THE HYDROCARBON RADICAL OF A NATURALLY OCCURING FATTY ACID RCOOH, WHERE M IS AN INTEGER FROM 2 TO 5, AND WHERE N IS AN INTEGER FROM 1 TO 10, AN N-HYDROXYALKYL DERIVATIVE OF SAID COMPOUND WHEREIN THE HYDROXYALKYL GROUPS CONTAIN A TOTAL OF 2 TO 10 CARBON ATOMS, AND AN ETHANOLAMINE RESIDUE OBTAINED IN THE REACTION OF ETHYLENE OXIDE AND AMMONIA TO PRODUCE ETHANOLAMINES, AFTER DISTIALLATION OF LOWER BOILING ETHANOLAMINES FROM THE REACTION PRODUCTS, SAID RESIDUE HAVING EQUIVALENT WEIGHT WITHIN THE APPROXIMATE RANGE FROM 145 TO
 165. 